I used my new Digital Caliper to measure the 360's heatsink mounting holes. I need it for a mod I'm working on. I figured I would post them up here just in case other people needed them.
Basically the holes are 60mmx60mm, thats center to center. The heatsinks have a 11mm gap between them. The diaginal is 85mm. I used the backplate I cut off my Xbox's cage.
(couldn't get it to exact 60.00mm for the pic, but oh well)
Hope that helps someone!
I'll try and update later with more measurments, like hole diameter, CPU/GPU height, and whatever anyone wants.